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Correct me if I'm wrong...


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Okay so I am now the proud owner of the Skywatcher 1145p, not a bad little scope at all!

I've heard setting circles is really difficult with the lower EQs because of the limited divisions of the measuring dials, but I would like to give them a try anyway.

So I have spent most of this afternoon reading guides on Polar alignment and setting circles, I just wanted to report what I think I understand now and if theres anything wrong I'm sure one of you experienced bunch will be able to correct me :p so here goes:

Polar alignment: Ignoring what the telescope is doing completely I only need to focus on the altitude adjustment which should read about 52 for me as that is the latitude for leicester? Obviously if this is off (I'll find out later) you point at it according toward Polaris. Also the azimuth should be adjusted so the bottom of the head is pointed toward the NCP (Just off polaris? I did alot of reading!)

Setting Circles: I will use stellarium, once polar aligned, and slew to an object that I have the RA/DE settings for, and twist the numbered dial around so this information matches what I see. Then I assume by leaving the circle untouched now I can slew roughly towards an object using the numbered dial.

Okay so thats my understand, please correct me! ;) One question I would like to ask is the Dec scale is 0-90 going both ways, and the information on Stellarium is in the format of 1H10M10S / +48 degrees. But which way would I be going for +48?

Any help would be great, thank you SGL! :D

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Hi Karl,

In essence you're correct in what you say, the + in the declination indicates North of the celestial equator when you come to minus in declination it indicates south.

I must warn you that a lot of members here will tell you that the setting circles are not accurate enough to use successfully, don't be put off try it out and see how you get on. I have used them on my EQ3-2 mount and found that objects were in the FOV of a wide field eyepiece, alright not bang in the centre but close.

Good luck, let us know how get on.

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Your description of using setting circles seems accurate to me.

The main reason for inaccuracy of the setting circles is that it is difficult to mark fine divisions in the small circles on most scopes. Think of a school geometry protractor - measureing angles less than 1-degree requires a protractor that is large enough to see these marks (or a very expensive laser-engraved protractor!!!).

In the days before digital setting circles and goto, the setting circles were intended to get you 'close enough' and then you used a star chart and your eyepiece view to star hop if neccesary and get you to the object.

I was selling telescopes in 1992 when Meade first released the LX-200 (the first successful commercial GoTo) At that time, the 8" model sold for $3500 - and if you adjust for inflation, that's probably over $10,000 today. :D They were loud, noisy, not that accurate (compared to today's offerings) and Celestron scoffed at them --- then played catch up for five years or more.

Go ahead - do it 'old school' as the kids say. You will be fine and your knowledge of the sky and guiding/tracking skills will really benefit.

Dan

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In Declination the + denotes northern hemisphere and the minus southern.

You don't say whether your mount is motorized or not. If not the setting circle scales will be out of date the moment you've set them but not enough to matter if you lay them off (adjust them to match) a nearby known star before moving to your object.

Olly

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Fantastic replies Alan, Dan and Ollie.

Very encouraging, I'm not expecting pinpoint accuracy just abit of aid to add to star hopping and seeing its equatorially mounted, I would feel ignorant to, not at least give it a go :D

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Hi Karl

Just remember you have to re-calibrate the RA setting circle every time you want to change objects.

Always try and use a star as close as feasible to the object you want to find.

They do work quite well if they're big. The calibrations on smaller ones are less accurate.

Good luck.

Steve

ps. On some mounts the Dec pointer has to be fine tuned the first time you use it.

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Yes I think I understand, olly. I kind of badly explained that, so I would use Stellarium as my reference to find a known star and then set the ring accordingly so my circle is then upto date, once upto date, I wouldn't touch it again unless it wasn't accurate enough :D

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Yes I think I understand, olly. I kind of badly explained that, so I would use Stellarium as my reference to find a known star and then set the ring accordingly so my circle is then upto date, once upto date, I wouldn't touch it again unless it wasn't accurate enough :D

Well, if you are motorized and well polar aligned then one setting of the setting circles on a known star would, in theory, be all you'd need. But if you are not motorized the sky will continue to turn (or, as you know, the Earth will continue to do so!!) but your setting circles will not, so the shelf life of your settings based on the known star is short. Strictly speaking, infinitely short. But the shelf life may get you to your first object. For a second object you will need to choose a second nearby star, re set the circles, and quickly hop to your next object. This, you see, is why (almost) no-one actually does it!

Olly

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Ah yes, I won't be using motor, just helps get used to the motions of a equatorial, also helps with understand the motion of the sky ;) I have done some star hopping already making routes its just nice to know a few methods for locating objects, I think for familiar objects, star hopping is easier but its nice to have alternatives too, plus in the future will not panic when I saved up for a HEQ5 or something :D Thanks for your help, tis much appreciated! :p

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I wouldn't think that being motorised would make a difference - the hand control does the same thing as a motor :D.

On my eq1 the dec scale slips round as well, so is fairly random :p. I also removed the RA scale pointer as I was finding that the dec locking knob was hitting it whilst I was looking at Saturn, before reaching the meridian.

This meant there was about an hour where I couldn't follow Saturn with the 'Eastern' orientation of the mount, and Saturn wasn't far enough west to use the 'Western' orientation ;)

Edited by Adrian
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I wouldn't think that being motorised would make a difference

On my eq1 the dec scale slips round as well, so is fairly random

First off your right, it will not matter if its motorised or not. The RA circle should not move round with the scope else how could you index anything? :D

Every time you moved the scope the setting circle would move with it.:p

On all the Equatorials I have had the Dec was fixed but the pointer had a little bit of adjustment so you could fine tune.

Regards Steve

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Yes I think I understand, olly. I kind of badly explained that, so I would use Stellarium as my reference to find a known star and then set the ring accordingly so my circle is then upto date, once upto date, I wouldn't touch it again unless it wasn't accurate enough :p

almost there :D

so you point your scope at vega and set it to the correct RA and dec at 1am exactly, in order to find vega in exactly one hours time you leave the dec setting as before, but you will need to turn your scope to its RA + 1 hour.

Ok so hypothetically if its 1am and vega is at 7hr RA / 30 dec, at 2am it will still be at 30 dec, but it will have shifted to 6hr according to your setting circles (assuming that you dont re-adjust them in the meantime).

so # minutes after setting your circles you need to subtract that amount from the settings that stellarium tell you, in order to find it (i think thats right, im pretty sure you minus the time...?)

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If you point your scope at vega and set the setting circles to the right coordinates, you then lock the R A setting circle whilst you are looking at vega, you wont need to lock the dec setting circle as it only moves in R A. When you look for something else you unlock the R A, then move your scope to the coordinates of whatever you are looking for then lock it again.

Hope this helps

steve

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almost there :D

so you point your scope at vega and set it to the correct RA and dec at 1am exactly, in order to find vega in exactly one hours time you leave the dec setting as before, but you will need to turn your scope to its RA + 1 hour.

Ok so hypothetically if its 1am and vega is at 7hr RA / 30 dec, at 2am it will still be at 30 dec, but it will have shifted to 6hr according to your setting circles (assuming that you dont re-adjust them in the meantime).

so # minutes after setting your circles you need to subtract that amount from the settings that stellarium tell you, in order to find it (i think thats right, im pretty sure you minus the time...?)

I see! So making a mental note of the time of setting it, means you can logically work out where it should be by compensating the hour that you haven't changed, that makes perfect sense thanks! :p

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If you point your scope at vega and set the setting circles to the right coordinates, you then lock the R A setting circle whilst you are looking at vega, you wont need to lock the dec setting circle as it only moves in R A. When you look for something else you unlock the R A, then move your scope to the coordinates of whatever you are looking for then lock it again.

Hope this helps

steve

Thanks steve that is helpful it really starts to all fall into place... eventually :D

I notice your also from good ol' "Lesta", any tips on any good observation sites? :p

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Thanks steve that is helpful it really starts to all fall into place... eventually :D

I notice your also from good ol' "Lesta", any tips on any good observation sites? :p

where are you in leicester. there is a couple of us that go to a place called glooston, it's in between kibworth and market harborough we have been there a couple of times, we have also been to saddington resorvoir which is quite good but glooston, is a little better.

PM me if you feel like tagging along.

steve

Edited by stevelcfc
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